Wheel spin

An electric drivetrain designed to improve the efficiency of cars and trucks has been fitted for the first time to a demonstrator vehicle that will be unveiled later this month.

The system, which comprises four electric motors, one inside each wheel, was developed by Quebec company TM4, and was ordered by Peugeot last year. The carmaker has installed the drivetrain on the Quark, a lightweight urban vehicle for two people that will debut at the Paris Motor Show.

A nickel-metal-hydride battery and fuel cell supplies electrical power to each of the wheel-motors, eliminating the conventional drivetrain including the transmission, the differential, the universal joints and the drive-shaft.

While this saves considerable weight and space within the vehicle, TM4 has also taken the opportunity to improve the motor and control technology to further reduce weight and energy consumption, said TM4 spokeswoman Isabelle Phoenix.

‘TM4 motors utilise permanent-magnet technology, which helps reduce energy consumption and the size and weight of the motors,’ she said.

The motor wheel uses a brushless inverted rotor configuration that can be embedded inside a regular-sized wheel. An electronic control module handles and converts the electrical current between the battery and the motors. The system operates each motor independently, managing the wheel torque based on the way the driver steers, accelerates and brakes.

In regenerative braking, the electronic module makes it possible to recover the alternating current generated by the wheel, and transform it into direct current and return it to the battery.

‘The technology results in a light, compact and highly efficient unit. This system permits high-precision control and independent torque applied to each wheel while maximising regenerative braking capacity,’ said Phoenix.

Quark weighs 425kg and is capable of transporting one or two passengers at speeds up to 68mph. Each motor provides a maximum torque of 100Nm, a maximum output power of 7kW and a continuous output power of 2.5kW. Efficiency under continuous load at 950rpm is 96.3 per cent.

TM4 says its system could be configured for all types of electric vehicle power supplies, including battery-only or hybrid vehicles. ‘An electric drive can be used as a primary source or as power assist. An example is the use of motor-wheels on the rear wheels of a front wheel drive platform making the vehicle either a four-wheel drive or equipped with launch assist,’ said Phoenix.

She said TM4’s systems and components are well suited for use in a variety of vehicles other than the passenger car. These include light trucks, buses and industrial vehicles.

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